Analytical characterization of the Siemens Dimension EXL high-sensitivity cardiac troponin I assay

Abstract Background Siemens Healthcare Diagnostics has four commercially available assays on different analytical platforms using different methodologies to generate signal. We assessed the analytical performance of the Dimension EXL hs-cTnI assay (LOCI method) across different matrices and compared it to two different acridinium ester-based hs-cTnI assays (ADVIA Centaur and Abbott ARCHITECT). Methods The analytical sensitivity and precision below the 99th-percentile was determined for the Dimension EXL hs-cTnI assay. Method comparisons were performed between the Dimension EXL contemporary cTnI and the hs-cTnI assays, between different matrices for the EXL hs-cTnI assay (serum, lithium heparin and EDTA plasma), and between different hs-cTnI assays (EXL versus ADVIA Centaur or Abbott ARCHITECT) using non-parametric analyses. Results The limit of blank and detection were 0.9 ng/L and 1.7 ng/L, respectively, with imprecision of 5.8% at 8.6 ng/L and 3.2% at 47.5 ng/L. Comparison between the EXL contemporary cTnI and hs-cTnI assay (range: 2.6–4214 ng/L) yielded proportional lower concentrations for the hs-cTnI assay (slope = 0.86; 95%CI: 0.81 to 0.96, n = 40); however, there was no difference in concentrations below 100 ng/L between the assays (median difference = −2.7 ng/L; 95%CI: −9.8 to 9.3). Passing-Bablok regression analysis with EDTA plasma yielded proportionally higher concentrations with the EXL hs-cTnI versus Abbott hs-cTnI (slope = 1.45; 95%CI: 1.02–1.86, n = 40) with proportionally lower concentrations with EDTA versus lithium heparin plasma with the EXL hs-cTnI assay alone (slope = 0.93; 95%CI: 0.90 to 0.99, n = 40). Comparison with Abbott hs-cTnI concentrations below 100 ng/L in the three matrices, indicated that the EXL hs-cTnI assay yielded higher concentrations (median difference range: 3.4–9.4 ng/L), with differences also evident when comparing the EXL hs-cTnI assay to the ADVIA Centaur hs-cTnI assay. Conclusion The Siemens EXL hs-cTnI assay meets the analytical criteria for a high-sensitivity assay, with assay specific cutoffs important to maximize clinical performance.